Non-impact printers are coming into more frequent use as a result of the advances in the technology relative to such printers. One such type of printer is a xerographic printer in which light emitting diodes (LEDs) are enabled in a selected manner to create an image on a photoconductive surface by producing a plurality of dots which collectively combine to form the characters of a printed text. In such a device, an input is supplied to the electronics of a print head which controls the enabling of the LEDs so that the text being inputted will be reproduced on a charged xerographic surface in the form of an image. This image may be developed and transferred as is well known in the art.
One shortcoming of an LED xerographic type of nonimpact printer is that a discontinuity is created as a result of the movement of the xerographic surface relative to the LED array. An LED array of any substantial size is composed of a plurality of units or modules. Each module is made up of a number of rows of longitudinally extending LED sites and these modules are placed in tandem with one another so that an extended longitudinal row of LED sites is created along the length of the array. Each LED module is operated independently. The manner in which an array is operated involves simultaneously enabling the first LED of each module, then the second LED of each module, then the third, and so forth down the line in sequence. As these LEDs are being enabled in turn, the xerographic surface moves relative thereto so that the line of dots being formed is formed at an angle rather than along a straight line as would be the case if the xerographic surface were stationary. Normally, such an angle is not observable to the human eye until such time as the dot produced by the last LED of a module is compared to the dot produced by the first LED of an adjacent module. For example, the last dot produced by the first module would be adjacent to the dot produced by the first LED of the second module which was printed at a time t.sub.1, whereas the last dot of the first module was printed at t.sub.n, t.sub.n being the time required to enable all the LEDs of a module. In this period t.sub.n, the xerographic surface addressing the array will move a certain distance "d" and this movement will cause separation of the dot produced by the last LED of the first module from the dot produced by the first LED of an adjacent unit. This distortion is visible to the human eye and results in an unsightly format. Obviously, it would be desirable if such distortion could be eliminated.
Efforts have been made to compensate for the distortion caused by the combination of sequential enabling of the LEDs and the movement of the photoconductor. In one such attempt, the modules were placed at angles, i.e. tilted, relative to the longitudinal direction of the array. The problem with tilting the modules was that it presented an alignment problem.